An Internet protocol (IP) address is a unique address that certain electronic devices use in order to identify and communicate with each other on a computer network utilizing the IP standard. A static IP address is an unchanging IP address that a computer uses every time it connects to a network such as the Internet. With a static IP address, a computer's identity can be easily identified by others; that way, for example, a website, email server, or other type of server connection can be hosted.
A dynamic IP address, on the other hand, is an IP address that is assigned to a computer, usually by a remote server that acts as a dynamic host configuration protocol (DHCP) server. IP addresses assigned using DHCP may change depending on the addresses available in the server set scope.
Currently existing dynamic IP address information has been manually collected and maintained. For example, a conventional dynamic IP list contains a list of dialup IP addresses, and may contain other dynamic IP addresses such as digital subscriber line (DSL) and cable user IP address ranges. Manually maintaining such a large list requires enormous effort and resources. Moreover, updating the list of dynamic IP addresses relies on the reporting of system administrators. With Internet topology and IP address assignments changing rapidly, such lists can be expected to contain increasingly obsolete information and omit newly configured dynamic IP addresses.
A reverse domain name system (rDNS) database is another conventional collection of IP address information. Reverse DNS is a process that looks up the host name associated with a given IP address. An rDNS record translates an IP address into a host name, which may be used to infer the address properties. Despite the existence of DNS naming conventions and recent proposals on standardizing DNS name assignment schemes, not all domains follow the naming rules. In fact, it is estimated that nearly half of all IP addresses do not have rDNS records.